Imaging apparatus and imaging method

ABSTRACT

An imaging apparatus, comprising a focus controller that generates an evaluation value by extracting given signal components from an image signal, and carries out focus adjustment by calculating position of the focus lens where the evaluation value becomes a peak, a display that displays an image based on image data generated from the image signal, and a controller that, as initial image display after commencement of the continuous focus adjustment operation, executes display using the display based on image data corresponding to an image signal in which the evaluation value becomes a peak, from among image data that has been acquired during the focus adjustment operation.

Benefit is claimed, under 35 U.S.C. §119, to the filing date of priorJapanese Patent Application No. 2016-011156 filed on Jan. 23, 2016. Thisapplication is expressly incorporated herein by reference. The scope ofthe present invention is not limited to any requirements of the specificembodiments described in the application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging apparatus and imaging methodcapable of so-called continuous AF (Auto Focus), whereby focusadjustment to move a focus lens based on imaging signals of an imagesensor that forms an image of a subject is carried out repeatedly.

2. Description of the Related Art

Conventionally, contrast AF, in which an evaluation value (also calledcontrast value) is calculated based on image signals from an imagesensor while moving the focus lens (called “scan operation”), and focusadjustment is carried out to a position of a focus lens where thisevaluation value becomes a peak, has been used in an imaging apparatus.Also, in contrast AF there is single AF where focus adjustment iscarried out once in response to half pressing of a release button etc.,and continuous AF (hereafter referred to as “C-AF”) where the single AFis executed repeatedly.

Since contrast AF is executed each time readout of an image signal iscarried out from the image sensor, improvement in AF speed is achievedby making a frame rate high-speed (refer, for example, to Japanesepatent laid open number 2013-025107 (hereafter referred to as patentpublication 1), and Japanese patent laid open number 2012-060371(hereafter referred to as patent publication 2)). Also, for display whencarrying out burst capture (repeatedly shooting continuously) togetherwith carrying out focus adjustment using C-AF, Quickview Display that iscarried out based on image data that has been acquired using burstcapture (called Quickview burst capture), or live view display that iscarried out based on image data read out from the image sensor at aframe rate, are performed.

SUMMARY OF THE INVENTION

An imaging apparatus of a first embodiment of the present invention, forcarrying out focus adjustment by moving a focus lens based on an imagesignal of an image sensor for forming a subject image, comprises a focuscontroller that generates an evaluation value by extracting given signalcomponents from the image signal, and carries out focus adjustment bycalculating position of the focus lens where the evaluation valuebecomes a peak, a display that displays an image based on image datagenerated from the image signal of the image sensor, and a controllerthat executes to display an image using the display by generating imagedata based on an image signal that has been acquired during a focusadjustment operation where continuous focus adjustment is executed bythe focus controller, wherein the controller, as initial image displayafter commencement of the continuous focus adjustment operation,executes display using the display based on image data corresponding toan image signal in which the evaluation value becomes a peak, from amongimage data that has been acquired during the focus adjustment operation.

An imaging apparatus of a second embodiment of the present invention,for carrying out a focus adjustment operation by moving a focus lensbased on an image signal of an image sensor for forming a subject image,comprises a focus controller that generates an evaluation value byextracting given signal components from the image signal, and carriesout focus adjustment by calculating position of the focus lens where theevaluation value becomes a peak, a tracking circuit that carries out atracking operation based on image data generated from an image signal ofthe image sensor, and a controller that causes execution of a trackingoperation by the tracking circuit by generating image data based on animage signal that has been acquired during a focus adjustment operationwhere continuous focus adjustment is executed by the focus controller,wherein the controller causes execution of a tracking operation by thetracking circuit using image data corresponding to an image signal inwhich the evaluation value becomes a peak, from among image data thathas been acquired during the focus adjustment operation.

An imaging method of a third embodiment of the present invention, forcarrying out focus adjustment by moving a focus lens based on an imagesignal of an image sensor for forming a subject image, comprisesgenerating an evaluation value by extracting given signal componentsfrom the image signal, and carrying out focus adjustment by calculatingposition of the focus lens where the evaluation value becomes a peak,and displaying an image using a display by generating image data basedon an image signal that has been acquired during a focus adjustmentoperation where continuous focus adjustment is executed, wherein whendisplaying the image on the display, as initial image display aftercommencement of the continuous focus adjustment operation, display isexecuted using the display based on image data corresponding to an imagesignal in which the evaluation value becomes a peak, from among imagedata that has been acquired during the focus adjustment operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram mainly showing the electrical structure of acamera of one embodiment of the present invention.

FIG. 2 is a drawing showing a sequence during burst shooting in a casewhere release priority has been set, in one embodiment of the presentinvention.

FIG. 3 is a drawing showing a sequence during burst shooting in a casewhere release priority is unset, in one embodiment of the presentinvention.

FIG. 4 is a flowchart showing continuous AF operation of the camera ofone embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments using a camera to which the present invention hasbeen applied will be described in the following in accordance with thedrawings. One preferred embodiment of the present invention is anexample applied to a digital camera as an imaging apparatus. This camerahas an image sensor, and focus adjustment is carried out by moving afocus lens based on an image signal (also referred to as “image data”)of the image sensor that forms a subject image. Also, a subject image issubjected to live view display on a display that is arranged on a rearsurface of a camera body, based on a converted image signal (imagedata). A photographer determines composition and photo opportunity bylooking at the live view display.

Also, if continuous AF is set, a scan operation of the photographinglens is invoked, an evaluation value (contrast value) based on an imagesignal (image data) from the image sensor at this time is acquired, anda history of times when an in-focus position is reached and the in-focuspositions of the focus lens, where this contrast value become a peak, isstored. At the time of release operation, and at the time of subsequentcontinuous shooting, in-focus position at the time of actual exposure ispredicted taking into consideration time lag, based on the focushistory. If image data is acquired by actual exposure, this image datais subjected to image processing and stored in a storage medium. Imagedata that has been stored in the storage medium can be subjected toplayback display on the display section if playback mode is selected.

Also, if continuous shooting mode has been set, actual exposure isexecuted at given time intervals, and image data is acquired and storedin a storage medium. Between each of the actual exposures, a scanoperation is executed, and actual exposure is executed at a focus lensposition where the evaluation value becomes a peak. During a scanoperation, if image data for a single frame is acquired when the focuslens passes through the vicinity of a focus prediction position, displayis performed on the display based on image data at this time. Display isnot carried out for frames other than this frame, and a single colorimage such as a black image is displayed on the display.

FIG. 1 is a block diagram mainly showing the electrical structure of acamera of one embodiment of the present invention. The camera of thisembodiment comprises a camera body 200 having an image sensor, and aninterchangeable lens 100 that is removably attached to this camera body200. With this embodiment, an interchangeable lens is exemplified, butit is also possible to fix a lens barrel to the camera body.

A photographing lens 101, motor drive section 102, lens control section103, memory 104 and a lens communication section 105 are provided withinthe interchangeable lens 100. The photographing lens 101 includesoptical lenses such as a focus lens and a zoom lens, and forms a subjectimage using a photographing optical system constructed using theseoptical lenses. The motor drive section 102 has a drive source such as amotor, and a motor drive circuit etc., and causes the focus lens to movealong the optical axis direction of the photographing optical system.

The lens control section 103 is constituted by a lens CPU and itsperipheral circuits. The lens CPU carries out control of each sectionwithin the interchangeable lens 100 in accordance with programs storedin the memory 104 and control instructions from a body CPU within thebody controller 204 at the camera body 200 side. The lens controlsection 103, for example, carries out control such as controllingmovement of the focus lens of the photographing lens 101 via the motordrive section 102 in accordance with instructions from the bodycontroller 204, and control of a scan operation of the focus lens anddrive to a focus position etc. Also, lens state, such as currentposition of the focus lens or zoom lens, scan operation in progressetc., and information inherent to the lens etc. is transmitted as lensdata to the camera body 200 side by means of the lens communicationsection 105.

The lens communication section 105 has a communication circuit, andcarries out communication with the camera body 200. Specifically, if theinterchangeable lens 100 is attached to the camera body 200, connectionis made with the body communication section 206 of the camera body 200and communication between the lens control section 103 and the bodycontroller 204 becomes possible.

Within the camera body 200 there are an image sensor 201, a liquidcrystal display 202, memory 203, body controller 204, operating section205, and body communication section 206. An image sensor 201 is arrangedon the optical axis of the photographing lens 101 close to an imagingposition of a subject image, and outputs image data (also called animage signal) obtained by photo-optically converting a subject imageusing a plurality of pixels arranged in a two dimensional array to thebody control section 204.

The body controller 204 is constituted by a body CPU and its peripheralcircuits. The body CPU carries out overall control of the camera inaccordance with programs stored in the memory 203. Various circuits suchas an image processing section, compression and expansion section andcommunication section etc. are provided as peripheral circuits withinthe body controller 204, in order to carry out processing of image dataand the like in cooperation with the body CPU. There are also a focuscontroller 204 a and a tracking section 204 b as peripheral circuits.

The focus controller 204 a has an evaluation value calculation circuit,and acquires an evaluation value (contrast value) for a subject image bybeing input with image data from the image sensor 201 and acquiring adifference signal between adjacent pixels. Also, this focus controller204 a carries out focus adjustment, in cooperation with the body CPU, tomove the focus position of the focus lens to an in-focus position bymeans of the lens control section 103 and the motor drive section 102.This focus controller 204 a functions as a focus controller thatgenerates an evaluation value by extracting given signal components fromthe image signal, and carries out focus adjustment by calculatingposition of the focus lens where the evaluation value becomes a peak.

The tracking section 204 b has a tracking circuit, and tracks positionof the same subject by comparing image data of a plurality of framesthat have been output from the image sensor 201. For example, it ispossible to track the same person who has been detected by a facedetection section or the like. The user may also set a subject that theywish to track by a manual operation. The tracking circuit in thetracking section 204 b functions as a tracking circuit for carrying outa tracking operation based on image data that has been generated from animage signal of the image sensor.

The body controller 204 functions as a controller that displays an imageusing the display by generating image data based on an image signal thathas been acquired during a focus adjustment operation where continuousfocus adjustment is executed by the focus controller. This controllerexecutes display of image data corresponding to an image signal forwhich an evaluation value has been made a peak by the focus controller,among image data that has been acquired during a focus adjustmentoperation, as initial display after commencement of a continuous focusadjustment operation, on the display (refer, for example, to time t5-t6in FIG. 2 and FIG. 3).

Also, after having executed the initial display using the display, thecontroller does not execute to display for a given period (refer, forexample, to time t7-t10 in FIG. 2 and FIG. 3). Image data correspondingto an image signal in which the evaluation value has become a peak is apredicted in-focus frame (refer, for example, to time t5-t6 in FIG. 2and FIG. 3, and predicted in-focus position IF in the graphs).

Also, the body controller 204 functions as a controller that generatesimage data based on an image signal that has been acquired during afocus adjustment operation, where a focus adjustment operation isexecuted continuously using a focus controller, and executes a trackingoperation using a tracking circuit. This controller causes execution ofa tracking operation by the tracking circuit using image datacorresponding to an image signal in which the evaluation value becomes apeak by the focus controller, from among image data that has beenacquired during the focus adjustment operation.

The memory 203 within the camera body 200 has various memory such asvolatile rewritable memory such as RAM, non-volatile rewritable memorysuch as flash memory, and removable storage media etc. Besides programsfor the body CPU, which were described previously, various data foradjustment are stored in the nonvolatile memory. Image data for takenimages that have been subjected to image processing by the bodycontroller 204 are stored in a storage medium. Also the memory 203detects a time for executing a scan operation to detect a focus lensposition at which contrast of an image becomes a peak, and stores thistime. The function of storing focus history may also be fulfilled by atemporary storage section (not shown) incorporated into the bodycontroller 204.

A liquid crystal display 202 has a liquid crystal monitor that isarranged on a rear surface or the like of the camera body 200. Live viewdisplay based on image data from the image sensor 201, playback displaybased on taken image data that has been read out from the memory 203,and display of menu images etc. for setting various shooting modes, arecarried out on the liquid crystal display 202. In a case where C-AF andcontinuous shooting mode have been set, then as has been describedabove, an image that is based on image data that has been acquired inthe vicinity of an in-focus position is displayed. The monitor is notlimited to a liquid crystal monitor, and another monitor such as organicEL may also be used, and may be arranged on other than the rear surfaceof the camera body 200. The liquid crystal display 202 functions as adisplay for displaying an image based on image data that has beengenerated from an image signal of the image sensor.

The operating section 205 includes various operating members such as arelease button, power supply button, menu button, OK button, and a crossshaped button, and operating states of these operating members areoutput to the body controller 204. The body controller 204 executescamera control in accordance with operation signals from the operatingsection 205. Various settings, such as various mode settings likecontinuous shooting mode and continuous AF mode, setting of continuousshooting speed (number of shot frames at the time of continuousshooting) when continuous shooting mode is set, release priority modeetc. are carried out on menu screens etc. In the case where theabove-described release priority mode is on, priority is given tocontinuous shooting using the continuous shooting speed even if focushas not been achieved (refer to FIG. 2, which will be described later),while if the release priority mode is off, shooting (actual exposure) isnot executed if a focused state has not been achieved (refer to FIG. 3,which will be described later).

The body communication section 206 has a communication circuit, andcarries out communication with the interchangeable lens 100.Specifically, if the interchangeable lens 100 is attached to the camerabody 200, the body communication section 206 establishes connection withthe lens communication section 105 within the interchangeable lens 100and communication between the lens control section 103 and the bodycontroller 204 becomes possible.

Next, a display operation for a subject image in a case where C-AF andcontinuous shooting mode of this embodiment have been set (continuousshooting C-AF) will be described using FIG. 2 and FIG. 3.

FIG. 2 shows a sequence during continuous shooting in a case where therelease priority mode has been set to on. The horizontal axis in thegraph shown in FIG. 2 represents change in time, while the vertical axisrepresents the position of a focus lens, with a dashed line representingpredicted in-focus position IF and a solid line representing movementposition L of the focus lens. The headings in the upper part of FIG. 2show, from the top, times (t1-t39), frame number FL, display suggestedimage period DT, and display frame DF.

FIG. 2 shows a sequence during continuous shooting, and actual exposure(actual shooting) is already being executed before time t1. Aftercompletion of the previous actual exposure, the period from time t1-t10is a scan operation period, in which the focus lens is moved from theinitial position for the purpose of the scan operation. During thisoperation exposure is performed at given intervals determined based onframe rate, and image data for a single frame is read out from the imagesensor 201 once an exposure time has elapsed.

In FIG. 2, if image data corresponding to frame No. 1 is read-out, anevaluation value for contrast AF is calculated. However, since at thispoint in time a subject was not in-focus in this frame, display of asubject image on the liquid crystal display 202 is not carried out, andonly a single color image, such as a simple black image, is displayed.After that, similarly, calculation of evaluation values and display ofsingle color images is also carried out for frame Nos. 2-4 (from time t2to t4). It should be noted that hatched frames shown in the displayframe DF section in FIG. 2 represent read-out image data that is used inevaluation value calculation but is not used in display.

In FIG. 2, image data that has been read out corresponding to frame No.5 (time t5-t6) is image data that has been formed in the vicinity of apredicted in-focus position. The predicted in-focus position is aposition that has been predicted to be an in-focus position this timebased on focus history, specifically a history of times when in-focusposition has been reached and in-focus position of the focus lens. Ifthe subject is not moving in a distance direction, then in-focusposition becomes the same as the previous in-focus position. An imagethat has been exposed at the predicted in-focus position has a highpossibility of being in focus, and is therefore acquired as image datafor display on the liquid crystal display 202 (referred to display frameDF in FIG. 2).

In the event that image data was not incorporated in frame No. 5, imagedata is acquired in frame No. 6 (time t6-t7) and an image is displayedon the liquid crystal display 202. It should be noted that “acquired”frames shown in the display frame DF section in FIG. 2 representread-out image data that is used in evaluation value calculation and isalso used in display.

Next, in frame No. 7 (time t7-t8) image data corresponding to this framenumber is read out, and an evaluation for contrast AF is calculated inorder to carry out detection of an evaluation value peak. Since, at thispoint in time, the lens is not at a predicted in-focus position, displayof a subject image on the liquid crystal display 202 is not carried out,and only a single color image, such as a simple black image, isdisplayed. Subsequently, for frame Nos. 8 and 9 also (time t8-t10),similarly, calculation of evaluation value for peak detection anddisplay of a singe color image are carried out.

If image data has been acquired for frame Nos. 1-9, it is possible todetect a peak of evaluation value joined this time, and on the basis ofthis it is possible to obtain an in-focus position of the focus lens forthis time. Then, in the period from time t10-t20 the shutter is closed,and lens drive to the in-focus position is carried out. Specifically, amechanical shutter (not illustrated) is closed, and the in-focusposition is calculated. If an in-focus position has been calculated, thebody controller 204 (focus controller 204a) causes the focus lens to bemoved to the in-focus position by means of the lens control section 103and the motor drive section 102 (arriving at the in-focus position att19).

Once the focus lens has arrived at the in-focus position, the mechanicalshutter is opened and actual exposure is commenced (time t20). Exposuretime for the actual exposure is determined using shutter speed that hasbeen set automatically or manually. Once the exposure time has elapsed(at time t21), the mechanical shutter is closed and image data is readout from the image sensor 201. If read-out times for image data of eachframe during the scan operation (time t1-t10) are compared, a highnumber of pixels are read out, and so read out time is long.

Also, in order to carry out the scan operation the body controller 204(focus controller 204a) causes movement of the focus lens to the initialposition by means of the lens control section 103 and the motor drivesection 102 (arriving at the initial position at time t22).

Once time t31 is reached, where the focus lens has arrived at theinitial position, then shooting is repeated, in the same way as thatpreviously described for time t1. Specifically, the scan operation (timet31-t40) is carried out, and once the scan operation is complete shutterdrive and lens drive are carried out to carry out actual exposure.

In this way, with this embodiment, in a scan operation during continuousshooting, image display is carried out based on image data that has beenacquired in the vicinity of a predicted in-focus position for the focuslens, and image display is not carried out based on image data that hasbeen acquired after that.

Therefore, with this embodiment, a through image display period forduring the scan operation (time t1-t10) is divided into three periods,namely a display not suggested period 1, a display suggested period, anda display not suggested period 2, and processing of image data that hasbeen read out from the image sensor 201 is made different for therespective periods.

The display not suggested period 1 (time t1-t5) is a period fromcommencement of the scan operation until before an in-focus frame (frameNo. 4). In this period, read out of image data from the image sensor 201is carried out, but while this image data is used in calculation ofevaluation value for contrast AF, it is not used in through imagedisplay in the liquid crystal display 202. It should be noted that imagedata read out from the image sensor 201 is subjected to thinningprocessing for use in evaluation value calculation, during the scanoperation.

This display not suggested period 1 corresponds to region A in FIG. 2,and in this period there is a state of significant boke even if asubject image is displayed. If a subject image with significant boke isdisplayed the user may be disconcerted, and so a through image is notdisplayed on the liquid crystal display 202, and the single color imagesuch as a simple black image is displayed.

The display suggested period (t5-t7) is a period of in-focus frames. Inthis period the focus lens is in the vicinity of a predicted in-focusposition, and read out of image data from the image sensor 201 isperformed. This image data that has been read out is used in calculationof evaluation value for contrast AF, and is also used in through imagedisplay on the liquid crystal display 202. As was described previously,the predicted in-focus position is a position that has been predicted tobe an in-focus position this time based on focus history, specifically ahistory of times when in-focus position has been reached and in-focusposition of the focus lens. Therefore, images used for display that havebeen acquired in the display suggested period are images that have ahigh possibility of being in focus, and that are suitable for the userto monitor the subject image.

The display not suggested period 2 (t7-t10) is a period after anin-focus frame, and before a period of shutter drive and lens drive. Inthis period, similarly to the not suggested period 1, read out of imagedata from the image sensor 201 is carried out, but while this image datais used in calculation of evaluation value for contrast AF, it is notused in through image display on the liquid crystal display 202. Thisdisplay not suggested period 2 corresponds to region B in FIG. 2, and inthis period there is a state of significant boke even if a subject imageis displayed. If a subject image with significant boke is displayed theuser may be disconcerted, and so a through image is not displayed on theliquid crystal display 202, and only a single color image such as asimple black image is displayed, or keep display of an image that wasincorporated in the display suggested period continues. It should benoted that in a case where it is not possible to acquire image data fordisplay in the suggested period, incorporation is made permissible.

Next, a continuous shooting sequence for a case where the releasepriority mode has been set to off will be described using FIG. 3. Thehorizontal axis in the graph shown in FIG. 3 represents change in time,while the vertical axis represents position of the focus lens, withdashed lines representing predicted in-focus position IF and realin-focus position RF, and a solid line representing movement position Lof the focus lens. The headings in the upper part of FIG. 2 show, fromthe top, times (t1-t31), frame number FL, display suggested image periodDT, and display frame DF.

In the event that release priority mode has been turned off also, untiltime t10 subject image display is performed in the same way as in thecase where the release priority mode is turned on. Specifically, throughimage display is carried out based on image data that has been acquiredin a case where the focus lens is at a predicted in-focus position, andthrough image display is not carried out based on image data that hasbeen acquired at other positions. However, while image data that hasbeen acquired in frame No. 5 (time t5-t6) is at a predicted in-focusposition, it is not at a real in-focus position, and so an image forthrough image display is blurred.

The case where release priority mode is turned on and the case whererelease proxy mode is turned on differ in terms of the processing fortime t10-t18. Specifically, in the case where release priority mode isoff it is a focus priority mode, and so until a focused state isachieved image data is repeatedly read out from the image sensor 201,calculation of evaluation value is carried out, and detection of anevaluation value peak continues.

With the example shown in FIG. 3, a real in-focus position RF is offsetfrom a predicted in-focus position IF, which means that an evaluationvalue will not become a peak in the vicinity of time t5. Therefore, inthe period from time t10-t18 image data is read out from the imagesensor 201 at given intervals in accordance with frame rate, andcalculation of evaluation value continues. Also, at the same time,through image display is also carried out based on image data that hasbeen read out. As was described previously, an image that is acquired ata predicted in-focus position and displayed is blurred, and so from timet10 onwards through image display is carried out every time image datais acquired. Specifically, through image display is performed for allimage data.

With the example shown in FIG. 3, since evaluation value based on imagedata that has been acquired in the vicinity of time t16-t17 reaches apeak, an image for through image based on image data incorporated atthis point in time becomes in focus. At time t18, the fact that theevaluation value has passed its peak is detected, and so the scanoperation is stopped and shutter and lens drive are carried out. Afterthis time t18 the situation is the same as for the case in FIG. 2, andso detailed description is omitted.

The example shown in FIG. 3 is a case where the subject has movedsuddenly, and in-focus position changes as illustrated (refer to realin-focus position RF). For this type of subject, to obtain an image thatis in focus the release priority mode should be turned off, an in focusstate awaited, and then shooting carried out. Also, with thisembodiment, after the display not suggested period 2 (time t7-t10),shutter drive and lens drive are not commenced and calculation ofevaluation value for peak detection continues, and during this timethrough image display is carried out based on image data that has beenread out from the image sensor 201. As a result, it becomes possible toconfirm an in focus subject image at any time.

It should be noted that in FIG. 2 and FIG. 3, in obtaining in-focusposition a subject is tracked, and a position where this tracked subjectreaches a focused state may be made an in-focus position. Specifically,a tracking target is set based on image data, and if image data for thevicinity of a predicted in-focus position is output the tracking targetis tracked by the tracking section 204 b. An in-focus position may thenbe obtained using image data for part of this tracking target. Sincetracking is carried out using image data for the vicinity of a predictedin-focus position, image data in a significant boke state is not usedwhich means that it is possible to improve tracking performance. Itshould be noted that the tracking target may be determined using facedetection, or may be set by the user using a manual operation. Also, theterm “tracking” here refers to detection of movement in XY directionswithin a plane using movement vectors.

Next, continuous AF operation of this embodiment will be described usingthe flowchart shown in FIG. 4. If the release button is pressed downfully when continuous shooting mode is set, the processing flow forcontinuous AF shown in FIG. 3 is commenced.

If the flow for continuous AF is entered, first initial position driveis executed (S11). Scan control of step S15, which will be describedlater, is carried out, but at the time of commencing this scan controlthe focus lens position is driven to an optimum position (lens positioncorresponding to times t1 and t31 in FIG. 2 and FIG. 3). Specifically,in contrast AF evaluation value peak is detected, but at the time ofactual exposure (S21 which will be described later) the focus lens ismoved to a position corresponding to an evaluation value peak. Scan forcontrast AF preferably starts from a position slightly offset from anevaluation value peak position. In this step, therefore, drive isperformed so that a position that is slightly offset from the peakposition of evaluation value becomes the initial position, taking intoconsideration the drive direction of the focus lens up to that time.

If initial position drive has been carried out in step S11, exposureconditions for scan are next determined (S13). Here, exposure conditionsat the time of scan control carried out in step S15 are determined. Indetermining exposure conditions, image data for when actual exposure wascarried out the previous time, or image data for a live view image, isincorporated, brightness information is calculated from this image data,and exposure conditions during scan (for example electronic shutterspeed etc.) are determined.

If determination of exposure conditions has been carried out in stepS13, scan control is next carried out (S15). With continuous AF, actualexposure and scan control are repeated while the release button ispressed down fully, and with the scan control scan drive is carried outfor a given number of frames (9 frames in the example shown in FIG. 2)in accordance with continuous shooting speed at the time of continuousshooting mode setting. In this step S15, evaluation value is calculatedevery time image data is acquired from the image sensor 201 while movingthe focus lens

Also, as was described using FIG. 2 and FIG. 3 in the display suggestedperiod (time t5-t7), through image display of the subject image iscarried out based on image data that was acquired when the focus lenswas at the predicted in-focus position. Regarding the predicted in-focusposition, for a subject that has been made a tracking target by thetracking section 204 b, previous in-focus positions at the time ofactual exposure may be stored as a focus history, and the in-focuspredicted position may be determined based on this focus history. In theevent that there is no tracking, in-focus position for the previous timemay be substituted.

If the scan control of step S15 is completed, next calculation ofin-focus position is carried out (S17). This calculation of in-focusposition is carried out before commencement of drive of the focus lens,which in the example shown in FIG. 2 is after time t10. In this stepS17, in-focus position during actual exposure is predicted using a focushistory up to now and peak position of evaluation value that has beendetected during the scan operation of step S15, taking intoconsideration the continuous shooting interval until the actual exposureof step S21, which will be described later. It should be noted that themechanical shutter is temporarily closed.

If calculation of in-focus position has been carried out in step S17,next focus drive is executed (S19). Here, the body controller 204 drivesthe focus lens towards the in-focus position that was calculated in stepS17, by means of the lens control section 103 and the motor drivesection 102. This focus lens drive is carried out in the period t10-t19in FIG. 2.

If the focus drive of step S19 has been executed, actual exposure isnext carried out (S21). Here, exposure control is carried out at anaperture value and shutter speed etc. for achieving appropriateexposure, image processing is carried out on image data that has beenacquired by the image sensor 201 at this time, and image data that hasbeen subjected to this image processing is stored in the memory 203. Itshould be noted that with this actual exposure, the mechanical shutteris opened, and once actual exposure is complete the mechanical shutteris closed. This closed mechanical shutter is opened until the next scancontrol.

If actual exposure has been executed in step S21, it is next determinedwhether or not 2R is kept held (S23). As described previously, incontinuous shooting mode continuous shooting continues while the releasebutton is pressed down fully. In this step, it is determined whether ornot the 2nd release (2R) switch, that is linked to full pressing down ofthe release button, remains on.

If the result of determination in step S23 is that 2R is maintained,processing returns to step S11, where there is drive to the initialposition, in-focus position is predicted and actual exposure is carriedout, and continuous shooting continues. On the other hand, ifmaintaining of 2R does not continue, namely if the user's finger hasbeen taken off the release button, the processing flow for continuous AFis terminated.

In this way, with the one embodiment of the present invention, givensignal components are extracted from an image signal to generate anevaluation value, and focus adjustment is carried out by calculating aposition of the focus lens where this evaluation value becomes a peak(refer, for example, to the focus controller 204 in FIGS. 1, and S11-S19in FIG. 4). Also, there is a display (for example, the liquid crystaldisplay 202 in FIG. 1) that displays an image based on image data thathas been generated from an image signal of the image sensor, and animage is displayed using the display by executing a focus adjustmentoperation continuously and generating image data based on an imagesignal that has been acquired during the focus adjustment operation. Atthe time of this display, display is executed using the display byperforming initial image display, after commencement of a continuousfocus adjustment operation, based on image data corresponding to animage signal in which an evaluation value becomes a peak, among imagedata that has been acquired during a focus adjustment operation (refer,for example, to the controller 204 in FIG. 1, the suggested displayperiod of time t5-t6 in FIG. 2 and FIGS. 3, and S15 in FIG. 4). In thisway, when continuous shooting is carried out using C-AF also, it ispossible to optimally display a subject image, and it is possible forthe user to carry out accurate framing. In particular, it is possible toprevent display of a through image that has significant boke aftercommencement of the scan operation.

Also, with the one embodiment of the present invention, after carryingout initial image display based on image data corresponding to an imagesignal in which the evaluation value becomes a peak, display is notcarried out for a given period (for example, the period of t7-t10 inFIG. 2). In this way it is possible to prevent display of a throughimage having significant boke after carrying out initial image display.

Also, with the one embodiment of the present invention, image datacorresponding to an image signal in which the evaluation value becomes apeak is an in-focus predicted frame (refer, for example, to thepredicted in-focus position IF and suggested display period of timet5-t6 in FIG. 2). In this way, when carrying out initial image displayit is possible to display an image in an in-focus state.

Also, with the one embodiment of the present invention, in a case whereit is not possible to detect an evaluation value peak even if given scandrive is carried out (refer, for example, to frame Nos. 1-9 for timet1-t10 in FIG. 3), scan drive continues and an evaluation value isdetected, and image display is carried out for every frame based on theimage data that has been acquired at this time (refer, for example, totime t10-t18 in FIG. 3). In this way it becomes to carry out display ofan image that is in an in-focus state.

Also, with the one embodiment of the present invention, there is atracking circuit for carrying out a tracking operation based on imagedata generated from an image signal of the image sensor (refer, forexample, to the tracking section 204 b in FIG. 1). There is also acontroller that generates image data based on an image signal that hasbeen acquired during a focus adjustment operation, where a focusadjustment operation is executed continuously using a focus controller,and executes a tracking operation using the tracking circuit (refer, forexample, to the body controller 204). This controller causes executionof a tracking operation by the tracking circuit using image datacorresponding to an image signal in which the evaluation value becomes apeak by the focus controller, from among image data that has beenacquired during the focus adjustment operation. In this way, even if thesubject moves, when calculating a predicted in-focus position it ispossible to increase precision. Also, since tracking is carried outusing image data in which an evaluation value becomes a peak, that is,using image data that is focused and not image data that issignificantly blurred, it is possible to improve tracking performance.

It should be noted that with the one embodiment of the presentinvention, the focus controller 204 a and the tracking section 204 b areformed integrally with the body controller 204, but they may also beformed separately from the body controller 204. Also, the focuscontroller 204 a and the tracking section 204 b may have a hardwarestructure such as gate circuits generated based on a programminglanguage that is described using Verilog, and may also use a hardwarestructure that utilizes software, such as a DSP (digital signalprocessor). Suitable combinations of these approaches may also be used.

Also, an example has been described where some parts of the overallprocessing are processed as software by the body CPU within the bodycontroller 204, and other parts of the overall processing are processedin hardware, but this is not limiting, and it is possible to have all ofthe processing formed by carrying out software processing or hardwareprocessing.

Also, with the one embodiment of the present invention, an imagingdevice has been described using a digital camera, but as a camera it isalso possible to use a digital single lens reflex camera, a digitalsingle lens camera or a compact digital camera, or a camera for movieuse such as a video camera, and further to have a camera that isincorporated into a mobile phone, a smart phone, a mobile informationterminal, personal computer (PC), tablet type computer, game consoleetc. In any event, it is possible to apply the present invention to anydevice as long as it is for taking pictures and capable of setting aC-AF mode or a continuous shooting mode, or an application for the same.

Also, among the technology that has been described in thisspecification, with respect to control that has been described mainlyusing flowcharts, there are many instances where setting is possibleusing programs, and such programs may be held in a storage medium orstorage section. The manner of storing the programs in the storagemedium or storage section may be to store at the time of manufacture, orby using a distributed storage medium, or they be downloaded via theInternet.

Also, regarding the operation flow in the patent claims, thespecification and the drawings, for the sake of convenience descriptionhas been given using words representing sequence, such as “first” and“next”, but at places where it is not particularly described, this doesnot mean that implementation must be in this order.

As understood by those having ordinary skill in the art, as used in thisapplication, ‘section,’ unit,' ‘component,’ ‘element,’ ‘module,’‘device,’ ‘member,’ ‘mechanism,’ ‘apparatus,’ machine,' or ‘system’ maybe implemented as circuitry, such as integrated circuits, applicationspecific circuits (“ASICs”), field programmable logic arrays (“FPLAs”),etc., and/or software implemented on a processor, such as amicroprocessor.

The present invention is not limited to these embodiments, andstructural elements maybe modified in actual implementation within thescope of the gist of the embodiments. It is also possible form variousinventions by suitably combining the plurality structural elementsdisclosed in the above described embodiments. For example, it ispossible to omit some of the structural elements shown in theembodiments. It is also possible to suitably combine structural elementsfrom different embodiments.

What is claimed is:
 1. An imaging apparatus that carries out a focusadjustment operation by moving a focus lens based on an image signal ofan image sensor for forming a subject image, comprising: a focuscontroller that generates an evaluation value by extracting given signalcomponents from the image signal, and carries out focus adjustment bycalculating position of the focus lens where the evaluation valuebecomes a peak, a display that displays an image based on image datagenerated from the image signal of the image sensor, and a controllerthat executes to display an image using the display by generating imagedata based on an image signal that has been acquired during a focusadjustment operation where continuous focus adjustment is executed bythe focus controller, wherein the controller, as initial image displayafter commencement of the continuous focus adjustment operation,executes display using the display based on image data corresponding toan image signal in which the evaluation value becomes a peak, from amongimage data that has been acquired during the focus adjustment operation.2. The imaging apparatus of claim 1, wherein: the controller does notexecute display for a given period after having executed the initialdisplay using the display.
 3. The imaging apparatus of claim 1, wherein:image data corresponding to an image signal in which the evaluationvalue becomes a peak is image data of an in-focus predicted frame.
 4. Animaging apparatus that carries out a focus adjustment operation bymoving a focus lens based on an image signal of an image sensor forforming a subject image, comprising: a focus controller that generatesan evaluation value by extracting given signal components from the imagesignal, and carries out focus adjustment by calculating position of thefocus lens where the evaluation value becomes a peak, a tracking circuitthat carries out a tracking operation based on image data generated froman image signal of the image sensor, and a controller that causesexecution of a tracking operation by the tracking circuit by generatingimage data based on an image signal that has been acquired during afocus adjustment operation where continuous focus adjustment is executedby the focus controller, wherein the controller causes execution of atracking operation by the tracking circuit using image datacorresponding to an image signal in which the evaluation value becomes apeak, from among image data that has been acquired during the focusadjustment operation.
 5. An imaging method that carries out focusadjustment by moving a focus lens based on image signals of an imagesensor for forming a subject image, comprising: generating an evaluationvalue by extracting given signal components from the image signal, andcarrying out focus adjustment by calculating position of the focus lenswhere the evaluation value becomes a peak, and displaying an image usinga display by generating image data based on an image signal that hasbeen acquired during a focus adjustment operation where continuous focusadjustment is executed, wherein when displaying the image on thedisplay, as initial image display after commencement of the continuousfocus adjustment operation, display is executed using the display basedon image data corresponding to an image signal in which the evaluationvalue becomes a peak, from among image data that has been acquiredduring the focus adjustment operation.